Electron discharge tube and the like



J1me 1939- c. F. MlLLER ELECTRON DISCHARGE TUBE AND THE LIKE Filed March12, 1938 INVENTOR ay Patented June 20, 1939 Carl F. Miller, Emporium,Pa., assignor to Hygrade Sylvania Corporation, Salem, Mass., acorporation of Massachusetts Application March 12, 1938, Serial No.195,496

7 Claims.

Thisv invention relates to electron-discharge tubes and more especiallyto tubes of the evacuated type.

A principal object of the invention is to provide a novel method ofsupporting a getter within a radio tube. 1 Y

Another object is to provide a radio tube mount with a surroundingelectrostatic shield and with a getter suspension which also functionsto supplement the shield.

A feature of the invention relates to a getter carrier which may belocated remotely from the press or stem of the tube, whereby the metalparts of the mount may be heated without flashing the getter.

A further feature relates to a novel getter suspension whereby selectiveheating of the tube parts and the getter is more easily controlled.

A further feature relates to the novel organization, arrangement andrelative location of parts constituting an improved radio tube mount andgetter.

Other features and advantages not specifically enumerated will beapparent after a consideration of the following detailed descriptionsand the appended claims.

While the invention will be disclosed herein, as

embodied in certain specific forms and as incorporated in one particulartype of an electron discharge tube, it will be understood that this isdone merely for explanatory purposes and not by way of limitation.Accordingly in the draw- Fig. 1 is a vertical elevational view of ashield electrode and getter suspension according to the invention.

Fig. 2 is a cross-sectional view of Fig. 1 taken along the line 2-2thereof, as indicated by the arrows.

Fig. 3 is a modification of Fig. 1.

Fig. 4 is another modification of Fig. 1.

Fig 5 is a top plan view of Fig. 4.

Fig. 6 shows the assembly of Fig. 1 in a radio tube with its bombardingcoil in position.

Fig. 7 shows the tube of Fig. 6 with the getter fiash coil in position.

. Fig. 8 shows the bombarding coil and a getter flash coil as used witha radio tube having the shield arrangement of Figs. 4 and 5.

In the manufacture of such devices as evacuated radio tubes and thelike, it is the usual practice to subject the tube to a predeterminedexhaust schedule and after the enclosing bulb has been evacuated to acertain extent, the various metal parts contained therein are raised toa sufficiently high temperature to drive out occluded gases therefrom.As a final step in the evacuation of the tube, it is the usual practiceto flash or explode a substance for scavenging or gettering the residualgases within the tube. The material employed for this purpose isdesignated in the art as a getterfi. Consequently, it becomes importantto provide some sort ,of selective heating of the mount per se ascompared with the heating of the getter material, and various methods ofeffecting this selective heating have been proposed heretofore. Inaccordance with the present invention, the, getter material is .carriedby a getter support which forms or supplements one of the electrodes ofthe mountpreferably, a shield electrode thereof. Consequently, thesupport or carrier for the getter material performs its ordinaryfunction as a suspension and also as a supplement to the electrostaticshielding of the shield electrode. One typical arrangement that may beused is illustrated in Fig. 1 wherein the numeral I represents a metalcup-shaped electrode or shield such as is known in certain types ofradio tubes and. as disclosed for example in detail in applicationSerial No. 189,295, filed February 8, 1938. As shown in cross section inFig. 2, the electrode forms a single turn inductive loop and advantageistaken of this fact to heat the shield for driving out occluded gases andthe like. The shield I is provided with a cut-out or window 2 which maybe circular, rectangular or any desired shape. Positioned within thewindow 2 and in spaced relation to the border thereof, is acorrespondingly shaped metal member 3 which may, although notnecessarily, be of the same material as the shield I. The member 3 issuspended in spaced relation to the border of window 2, preferably by arelatively thin Wire 4 which may be welded to the shield l and t0 themember 3. The member 4 is preferablyof electrical conductive materialbut is chosen, either as to smallness of cross section or as tocomposition, to act as a comparatively poor conductor of heat withrespect to the conditions under which the shield I is later heated.Attached in any convenient manner to the member 3 is a relatively smallquantity of getter material 5 of any composition well known in the radiotube art. Preferably, although not necessarily, the member 3 is providedwith a central recess to receive the getter 5, and if desired, aperforate or porous cover may be welded to the member 3 to prevent thegetter material being accidentally dislodged, While permitting it to beflashed in the well known manner. As shown in Fig. 2, the member 3 maybe curved to form to the peripheral curvature of the shield, so that, sofar as electrostatic shielding action is concerned, the shield by reasonof the member 3 is peripherally and vertically complete except for therelatively minor spacing which exists between member 3 and the window 2.However, this spacing is so small as to have inappreciable effect on theelectrostatic shielding.

Fig. 6 shows in partial cross-section a typical radio tube embodying thecomposite shield and getter support of Figs. 1 and 2. This tube maycomprise an enclosing glass envelope 6 provided with a base I and withthe usual contact prongs 8. The mount is shielded by the shield I whichis supplemented by the rim of base I as described in application SerialNo. 189,295, filed February 8, 1938, it being understood that said rimis of metal and overlaps vertically the lower end of shield I. Supportedwithin the envelope 6 is any well known form of radio tube mountcomprising for example an electron-emitting cathode 9, at least one wirewound grid I and a plate or anode II. In the particular type of mountshown in Fig, 6, the control grid is provided with side rods I2, I3,which extend upwardly through the top of the shield I. The top of shieldI may be provided with a window I4 to allow the grid side rods to passthrough the shield without being shortcircuited, it being understood ofcourse that a suitable mica disc spacer I5 is employed for this purposein the manner well known in' the radio tube art. For a detaileddescription of a mount of this character, reference may be had to saidapplication Serial No. 189,295. The side rods I2, I3 may be connected bya strap I6 and thence to the usual top cap II.

The tube is subjected to any predetermined exhaust schedule during whichthe various metal parts are heated, preferably by electromagneticinduction, to drive out occluded gases and the like. Thus as indicatedin Fig. 6, a bombarding coil I8 is positioned around the tube, this coilbeing energized preferably by a high frequency alternating current so asto induce heating currents into shield I in the well known manner.Because of the poor heat conductivity of the member 4, the shield I canbe raised to an outgassing temperature without raising the gettermaterial 5 to flashing temperature. After the metal parts have been thusoutgassed, the bombarding coil I8 is removed and a small flash coil I9is positioned adjacent the member 3 as indicated in Fig. 7.'

The coil I9 is likewise energized by a high frequency alternatingcurrent so as to raise the member 3 to a sufficiently high temperature'to flash the getter 5 after which the tube may be sealed ofi in theusual manner.

Instead of positioning the getter carrier 3 midway of the height ofshield I, it may be positioned at the lower end thereof as indicated inFig. 3. In tubes where no top cap, corresponding to cap I! is employed,the getter carrier may be positioned at the top of the shield, thisarrangement being shown in Figs. 4, 5 and 8. With this arrangement, thebombarding coil land the flash coil I9 may be positioned coaxiallyinstead of at right angles, as is necessary with the embodiments ofFigs. 1 and 3. The arrangement of Fig. 8 also has the advantage that thegetter carrier 3 closes off the opening I4 in the top of the shield thusfurther enhancing the electrostatic shield, and there is very littledanger of the condensed flash material depositing on parts of the mountwhere' it will interfere with the proper operation of the tube. Themanner of bombarding the metal parts of the tube of Fig. 8 by the coilI8 and the manner of flashing the getter 5 by the coil I9, are similarto those describedin connection with Fig. 6. While the inventionhas'been described with the carrier 3 forming a part of the shield I, itwill be understood that it may form part of the plate electrode in anycase where the shield I is omitted.

Various changes and modifications may be made in the particularembodiments disclosed without departing from the spirit and scope of theinvention.

What I claim is:

l. A radio tube mount including a tubular metal electrode having anopening in the wall thereof, and a getter carrier mounted within saidopening.

2. A radio tube mount. according to claim 1 in which the getter carrieris mounted in spaced relation to the border of said opening.

3. A radio tube mount according to claim 1 in which the getter carrieris mounted within the opening in electrical conductive relation with theelectrode but in poor heat conductive relation.

4. A radio tube mount according to claim 1 in which said opening isintermediate the ends of said electrode.

5. A radio tube mount according to claim l-in which said opening is atthe lower end of said electrode.

6. A radio tube mount according to claim 1 in which the electrode is inthe form of a metal cup and the opening is in the transverse wall of thecup.

7. An electrostatic shield arrangement for a tube mount comprising. atubular metal shield having a window in a wall thereof, a metal membermounted within said window in slightly spaced relation to the borderthereof, said metal member carrying a quantity of getter material, andanother member electrically connecting the firstmentioned member to saidelectrode, said other member having a relatively lowheat conductivity.

CARL F. MILLER.

